By the time you're going to production, your vetted and locked dependency should be living in your own cache/mirror/vendored-repo/whatever so that you know exactly what code you built your project around and know exactly what the availability will be when you build/instantiate your project.
Your project shouldn't need to care whether GitHub fell out of fashion and the project moved to GitLab, and definitely shouldn't be relying on GitHub being available when you need to build, test, deploy, or scale. That's a completely unnecessary failure point for you to introduce.
Systems that use URL-identified packages can work around some of this, but just reinforce terrible habits.